1. Field of the Invention
The present invention deals with coke ovens and, in particular, with coke oven charging hole covers.
2. Description of the Prior Art
Coke ovens are conventionally filled with coal in preparation for the coking process through a plurality of charging holes located on the battery top. The removable covers for these charging holes have generally consisted of a single cast iron plate which rests on a frame surrounding the charging hole so as to form a peripheral gravity seal around the charging hole where the cover contacts the frame. These plates, however, are known to reach such high temperatures during the coking process that they may tend to warp, and if such warping does occur they may no longer form a gas tight seal with the charging hole frame. The escape of pollutants from inside the oven may, therefore, result. Furthermore, because heat is conducted more efficiently through these cast iron charging hole covers than through other sections of the oven roof, it is believed that this cast iron construction may be responsible for the occurrence of undersirable concentrations of heat directly above the covers. Various suggestions have been made for alleviating the above mentioned problems. U.S. Pat. No. 3,900,369, for example, proposes that a cover be constructed by bolting or otherwise fixing a preformed refractory plate section below an iron cover top section. While this cover would appear to reduce heat flow from inside the coke oven, it may, under certain circumstances, be preferable not to incur the costs involved in manufacturing a specially shaped, preformed refractory plate and fixing it to the iron cover. In particular, it is deemed advantageous from a cost perspective to use cast-in-place castable refractories in charging hole covers. It has been found, however, that conventional castable refractories may often not be sufficiently durable to be suitable for this use. Furthermore, even if a preformed refractory plate were used on a charging hole cover, such a charging hole cover might be subject to damage as it is continually removed from then replaced over the charging hole because of the relative brittleness of its refractory plate element. It is, therefore, the object of the present invention to provide a comparatively flexible, monolithic insulating charging hole cover which may be manufactured with relative ease and which does not require the production of any costly special refractory shapes.